A conventional reprographic system is the office copier. Traditionally, the copier, in the office equipment context, refers to a light lens xerographic copier in which paper originals are in fact photographed. The images are focused on an area of a photoreceptor, which is subsequently developed with toner. The developed image on the photoreceptor is then transferred to a copy sheet which in turn is used to create a permanent copy of the original.
In recent years, however, there has been made available what is known as digital copiers. In the most basic functions, a digital copier performs the same functions as a light lens copier, except that the original image to be copied is not directly focused on a photoreceptor. Instead, with a digital copier, the original image is scanned by a device generally known as a raster input scanner (RIS) which is typically in the form of the linear array of small photosensors.
The original image is focused on the photosensors in the RIS. The photosensors convert the various light and dark areas of the original image to a set of digital signals. These digital signals are temporarily retained in a memory and then eventually used to operate a digital printing apparatus when it is desired to print copies of the original. The digital signals may also be sent directly to the printing device without being stored in a memory.
The digital printing apparatus can be any known type of printing system responsive to digital data, such as a modulating scanning laser which discharges image wide portions of a photoreceptor, or an ink jet printhead.
Moreover, with the advent of the digitalization of the office copier, there has also been made available digital multi-function machines. The digital multi-function machine is a single machine which provides a user with more than one function. An example of a typical multi-function machine would include a digital facsimile function, a digital printing function, and a digital copy function.
More specifically, a user can utilize this digital multi-function machine to send a facsimile of an original document to a remote receiving device, to scan in an original image and print copies thereof, and/or to print documents from either a network source, locally connected source, or from a portable memory device which has been inserted into the multi-function machine.
An example of the basic architecture of a digital multi-function machine is illustrated in FIG. 2. As illustrated in FIG. 2, the architecture of the digital multi-function machine includes a scanner 3 which converts an original image into a set of digital signals that can be either stored or reproduced. The scanner 3 is connected to a central bus system 1 which may be either a single bus or a plurality of buses which provide interconnections and intercommunications between the various modules and devices on a multi-function digital machine.
The digital multi-function machine, as illustrated in FIG. 2, further includes a digital printing device 23 which converts digital signals representing an image into a hardcopy of that image on a recording medium whether the recording medium be paper, transparency, or other type of markable medium. The digital multi-function machine also includes a memory 21 for storing a variety of types of digital information such as machine fault information, machine history information, digital images to be processed at a later time, instruction sets for the machine, job instruction sets, etc.
In addition to the memory 21, a typical digital multi-function machine includes an electronic pre-collation memory section 7 which may store the digital representation of the image being presently rendered by the digital printing device 23. In the electronic pre-collation memory 7, the digital image is already laid out in its page structure so that it can be readily rendered by the digital printing device 23.
The digital multi-function machine as illustrated in FIG. 2, further includes a user interface 5 which allows the user to select the various functions of the multi-function machine, program various job attributes for the particularly selected function, provide other input to the multi-function machine as well as display informational data from the digital multi-function machine.
If the digital multi-function machine is connected to a network, the digital multi-function machine would include a network interface 19 and an electronic subsystem (ESS) controller 9 which would control the interrelationship between the various modules or devices on the digital multi-function machine and the network.
To enable a facsimile function, the digital multi-function machine would include, typically, a voice/data modem 11 and a telephone circuit board 13. Moreover, the digital multi-function machine may include input/output drives 17 such as a floppy disc drive, a CD ROM drive, a tape drive, or other type of drive which can accept a portable memory device.
In some digital multi-function machines, the machine also includes a finisher 29 which can perform certain operations upon the printed output from the printing device 23. Lastly, the digital multi-function machine includes a controller 15 which controls all the functions within the multi-function device so as to coordinate all the interactions between the various modules and devices.
FIG. 1 illustrates an overall construction of a digital multi-function machine. The digital multi-function machine, as illustrated in FIG. 1, includes a scanning station 35, a printing station 55, and a user interface 50. The digital multi-function machine may also include a finisher device 45 which may be a sorter, tower mailbox, stapler, etc. The printing station 55 may include a plurality of paper trays 40 that store the paper used in the printing process. Lastly, the digital multi-function machine may include a high capacity feeder 30 which is capable of holding large amounts of paper stock to be used by the machine.
In a typical scanning function, the operator would utilize the scanning station 35 to scan in the images from the original documents. This scanning station 35 may be a platen type scanner or may include a constant velocity transport system which moves the original documents across a stationary scanning device. Moreover, the scanning station 35 may also include a document handling system which is capable of placing the original documents, automatically, on the glass platen for scanning.
With respect to the printing functions, the printing station 55 would retrieve the proper paper from one of the multiple paper trays or the high capacity feeder, render the desired image on the retrieved paper, and output the printed image to the finishing device 45 for further operations.
The user interface 50 allows the user to control the various functions of the digital multi-function machine by presenting various types of screens to the user which provides the user an opportunity to program certain job characteristics or function characteristics.
One important function of a digital reprographic system, whether the system be a digital multi-function machine or digital copier, is locating the position of top edge or leading edge a copy substrate to be printed on. This is important in providing proper registration of the image onto the copy substrate. The locating of the top edge or leading edge of the copy substrate to be printed on is particularly important when printing in a duplex mode so as to ensure proper front to back registration on the copy substrate since the duplex path is usually longer than the simplex path. However, the locating of the top edge or leading edge of the copy substrate is equally important in a simplex path because of the many things that can affect the transportation of the copy substrate from its copy output tray to an image transfer station. There have been attempts to provide a means to locate the position of top edge or leading edge a copy substrate to be printed on; however, these attempts have failed to provide the proper registration that is needed to accurately print the image on the copy substrate.